Combustion train element and fuse for blasting and pyrotechnic and the like purposes, and method of preparation thereof



. ,such a manner that the fibres have acquired the a Patented July 4,153a cous'rron 'rnam ron s'rme THE o it; PURPOSES, AND METHODPREPARATION THEREOF ammun- No Drawing. Application August 14, 1936,Serial No. 96,118.- In Great Britain August 21, 1935 11 Claims.

This invention relates to the preparation of coherent combustion trainelements made from a fuse powder, e. g., blackpowder or blackpowdersubstitutes or constituents thereof, which elements may be used insubstitution for blackpowder impregnated cloth and the like forpyrotechnic and similar purposes, in blasting operations, and in thepreparation of safety fuse.

The present invention consists in a process for the manufacture ofcombustion train elements, according to which a fuse powder, e. g.,blackpowder or a mixture of ingredients thereof, in finely divided form,is suspended in an aqueous medium. saturated with respect to the water-,soluble components and is agitated with a proportion of a fibrillatedcellulose bonding material, whereupon the suspension is drained to forma wet felt which is then further dried and shaped. The proportion offibrillated cellulose bonding material is small relative to the weightof the fuse powder or fuse powder ingredients.

By the term fibrlllated cellulose bonding material as used herein and inthe appended claims we mean cellulose fibrous material which has beenbeaten or pulped in an aqueous medium in crushed or bruisedcharacteristics associated with the product of a blunt beating process.Unbeaten fibrous material, or material which has been beaten Withsharpblades so that the individual fibres are merely out without beingcrushed, does not usually possess felting properties suificiently goodto' justify its use for the purpose of the present invention.

The-term fuse powder as used herein and in the appended claims signifiesa material which, when in finely divided form, is capable of propagatingits own combustion along a train. For the purposes of the inventionthere may be used blackpowdersubstitutes, l. e., non-detonatingcombustible mixtures capable of production in granular or powderform'and classifiable in Classes 2 or 4 of the British List of AuthorisedExplosives, or the ingredients of such black-powder substitutes.Blackpowder itself, however, and the ingredients of blackpowder aremostfrequently suitable; and the invention is hereinafter described inrelation to blackpowder.

It is convenient that thesaturated aqueous solution of the water-solubleconstituent of the blackpowder'should contain a proportion of alcohol,or other easily evaporated neutral water.-

miscible organic liquid, inorder to depress the solubility of thewater-soluble constituent. The.

water-soluble constituent will usually consist of potassium nitrate,since blackpowders made with other salts are not usually employed indahemanufacture of combustion train elements on account of theirhygroscoplcity. An unduly high concentration of this ingredient in thesolution may militate against proper felting of the fibres, or may havea corrosive effect on metal parts of the apparatus or other undesiredeffects, but the presence of a proportion of the organic liquidconsiderably reduces the solubility of potassium nitrate. a

In preparing the felt; the finely divided solids and the fibrillatedcellulose bonding material are thoroughly mixed and dispersed in theaqueous suspension medium already saturated with the water-solubleconstituent, and the material is formed into a felt by filtering,screening or otherwise removing the bulk of the water. The material isadvantageously filtered through ascreen of fabric or metal gauze. Asuitable mesh for the gauze is about 20-100 per linear inch. Some of theremaining moisture may then'be removed by pressure or suction and thefelt subsequently transferred on a travelling screen or the like to adrying chamber where it is dried off at a suitable temperature such as40-50" 0., being supported by the screen at least until the moisturecontent has been greatly reduced. For further lightly twisted in orderto form a yarn-like element.

The formation of the felt may be carried out with the aid of machineryknown in the papermaking art but it may be necessary to provideadditional means for agitating the suspension to prevent deposition ofthe relatively compact and dense noncellulosic particles to the ,bottomof the reservoir from which the suspension passes to the screen orgauze. Various types and modifications of machinery are suitable for thepurpose, for instance cylinder metal machines, or Foudrinier machines.Continuous rotary filters may also be employed. It will be appreciatedthat the proportion of liquids to solids in the suspension shouldbechosen with regard to the type of machine employed.

Suitable cellulosic fibrous materials for use in ,themanufacture ofpyrotechnic combustion train elements, it has properties which render itsuitable for the preparation of a safety fuse.

' In the manufacture of safety fuse a strip or yarn of the blackpowderfelt is used as the core, around which the covering and counter yarns orother coverings are spun or positioned. In a spinning machine of theusual type, the motion of the covering yarnpulls the-core forward withit, so that it is only necessary to enter the end of the length of thefuse element in position.

Combustiontrain elements prepared from blackpowder dust in accordancewith our invention are characterized by a lower burning speed thangranular blackpowder or blackpowder dust, while combustion trainelements similarly prepared from the unincorporated ingredients ofblackpowder have a still lower burning speed. In the manufacture of slowsafety fuse, accordingly, the ingredients of the black-powder may beemployed without the expense of the usual operations of incorporationand granulation associated with the manufacture of blackpowder.

Safety fuse may be prepared according to our invention with a slowerregular burning speed than any other safety fuse of which we are aware.Safety fuse of regular burning speed lower than a speed corresponding'to250 seconds per yd. or

even lower than one corresponding to 300 seconds per yd. may thus beobtained. It is not claimed however that the safety fuse preparedaccording to our invention has the property of spitting like ordinarysafety fuse, and in its application it is usually necessary that thedetonator should contain in addition to the usual priming composition aloose charge of a substance which is particularly easy to ignite suchfor instance as lead dinitrocresolate, or lead sulpho-cyanate mixtures.For initiating blackpowder pellets, it is advisable that the fuse shouldbe capped with a perforated cap containing an igniting charge totransfer the ignition from the fuse to the blackpowder. Alternativearrangements for transferring the ignition will be obvious to thoseskilled in the art.

The proportion of cellulosic fibi e present in the felt cannot beindefinitely increased, since the combustion train element will ultimatebecome uncertain in its propagation combustion. The

precise maximum proportion which may be employed will be dependent on anumber of factors, including-the cross sectional area of the train andthe heat capacity of its environment. In the case of safety fuse, inwhich the element is naturally of.smal1 cross sectional dimensions andis surrounded by a considerable amount of heat-alrsorbing material, asuitable proportion of cellulose flbre is about 5-15% of the totalweight, and it is hardly possible to exceed this amount much withoutadverse eifect on the burning properties of the fuse. The use offibrillated cellulosic ma-.

terial, however, renders it possible to obtain a felt of the requisitestrength and coherency with such proportions of cellulose to.fuse powderor fuse' powder ingredients.

In the manufacture of other types of combustion train element it may bepracticable to use 2000 parts of aqueous alcohol of specific gravity0.9726 (obtained by mixing water and industrial spirits 66 O. P. in thevolumetric proportions 3: 1) are saturated with potassium nitrate by theaddition of 220 parts of nitrate, and the decanted saturated solution isplaced in the stuff chest of a cylinder mould machine provided withpaddles to overcome silting. 150 parts in all of the solid ingredientsemployed in the manufacture of ordinary blackpowder fuse powder areadded in such a state of division that they pass through a mesh B. S.sieve and there are also added 180 parts of a blunt beatensuspension ofkraft pulp which contains 18 parts of dry kraft pulp and 162 parts ofwater. A further 18 parts of potassium nitrate are added with the fusepowder ingredients in order to saturate the water introduced into thesystem in the form of the kraft pulp suspension.

The suspension is well mixed and .the wet felt deposited on the cylindermould is dried down to a moisture content of 10% and the sheet is cutinto portions whilestill containing this percentage of moisture. It isthen further dried down to a moisture content of about 1%. The thicknessof the sheet is approximately 90 thousandths of an inch.

Long strips of the material may be used either singly or twistedtogether as fuses or in place of Example 2 safety fuse from the sheetprepared as in Example 1. A suitable length of a core portion,consisting of a strip 1%" wide of the sheet produced according toExample 1, is introduced in place of the. core of loose granularblackpowder in a safety fuse machine in which three textilecounteringsare spun round it in the ordinary way.

The fuse is finished in the usual manner.

The burning speed of a fuse made in this way corresponded to 315-325seconds per yard. For purposes of comparison a fuse similarly fashionedfrom blackpowder dust in place of the strip of the core material of thepresent invention was found to have a speed corresponding to 105-110seconds per yard.

The fuse prepared according to Example 2 was suitable for use with adetonator provided with an auxiliary igniting charge of the leadsulphocyanate or lead dinitrocresylate type in addition to the usualpriming charge and secondary charge.

Example 3 The preparation was carried out as in Example 1, except thatinstead of the ingredients of 150 parts blackpowder there. were employed150 parts of blackpowder dust passing a 60 mesh B. S. sieve. When madeup into a safety fuse substitute as described in Example 2, it was foundthat 4a This example illustrates the production of a the safety fuse hada burning speed corresponding to about 105-110 seconds per yard.

Example 4 90 parts of blackpowder dust and 100 parts of wet pulped kraftpulp containing 10% of its weight of dry pulp were added to a mixture of80 parts of water and 20 parts of methylated spirits previouslysaturated with potassium nitrate and containing sufiicient undissolvedpotassium nitrate to saturate the water added in the form of the pulp.The whole mixture was agitated, screened and dried to form sheets ofabout 1 mm. in thickness. Before the sheet was quite dried, it was cutinto discs. The waste material from the cutting operation is returned tothe agitated pulp and reworked. The discs are suitable for use asdescribed in Example 1.

We claim:

1. A process of preparing combustion train elements, which comprisessuspending a black powder composition in an aqueous medium saturatedwith respect to the water-soluble components of saidcomposition,-agitating said suspension with a relatively smallproportion of a fibrillated cellulose bonding material, and removingsaid aqueous medium to form a felt.

2. A process of preparing combustion train elements, which comprisessuspending a black powder composition in an aqueous medium saturatedwith respect to the water-soluble components of said composition,agitating said suspensionwith 5 to 20% of a fibrillated cellulosebonding material, said percentage being calculated on the weight of thesolid content in said suspension, and removing said aqueous medium toform a felt.

3. A process of preparing combustion train elements, which comprisessuspending a black powder composition in an aqueous medium saturatedwith respect to the water-soluble components of said composition,agitating said suspension with 5 to 15% of a fibrillated cellulosebonding material, said percentage being calculated on the weight of thesolid content in said suspension, and removing said aqueous medium toform a felt.

4. A process of preparing combustion train elements, which comprisessuspending a black powder composition in aqueous alcohol saturated withrespect to the water-soluble components of said composition, agitatingsaid suspension with a relatively small proportion of a fibrillatedcellulose bonding material, removing said aqueous alcohol to form afelt.

5. A combustion train element consisting of a coherent felt of burningspeed lower than 250 seconds per yard, which felt comprises a blackpowder composition intermingled with a fibrillated cellulose bondingmaterial.

6. A combustion train element consisting of a coherent felt of burningspeed lower than 250 seconds per yard, which felt comprises a blackpowder composition intermingled with from 5 to 20% by weight of afibrillated cellulose bonding material.

7. A combustion train element consisting of a coherent felt of burningspeed lower than 250 seconds per yard, which felt comprises a blackpowder composition intermingled with from 5 to 15% by weight of afibrillated cellulose bonding material.

8. A combustion train element consisting of a coherent felt of burningspeed lower than 250 seconds per yard, which felt comprisesunincorporated black powder ingredients intermingled with kraft pulp.

9. A process of preparing combustion train elements, which comprisessuspending a black powder composition in an aqueous medium saturatedwith respect to the water-soluble components of said composition,agitating said suspension with a relatively small proportion of afibrillated cellulose bonding material, removing said aqueous medium toform a moist felt, shaping said felt into' the form of a core andenclosing in an envelope.

10. A safety fuse including a core of coherent felt of burning speedlower than 250 seconds per yard which felt comprises a black powdercomposition intermingled with fibrillated cellulose.

11. A safety fuse including a core of coherent felt of burning speedlower than 250 seconds per yard which felt comprises a black powdercomposition intermingled with 5 to 15% by weight of the fibrillatedcellulose.

JAMES S. B. FLENIIN RUSSELL CHARROSIN PAYN.

